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Bulletin of Botanical Research ›› 2020, Vol. 40 ›› Issue (5): 706-717.doi: 10.7525/j.issn.1673-5102.2020.05.009

• Research Report • Previous Articles    

Effect of Soak Stems Overnight with Deionized Water on Measuring Maximum Hydraulic Conductivity in Xylem of Stem Segments of Robinia pseudoacacia L. and Age-relate Difference

LIANG Zhao1, WEI Kai-Lu1, YANG Dong-Mei1, PENG Guo-Quan1,2   

  1. 1. College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004;
    2. Qinling National Botanical Garden, Xi'an 710061
  • Received:2019-10-10 Published:2020-07-10
  • Supported by:
    Natural Science Youth Foundation of Zhejiang Province(LQ16C030002);Project in Science and Technology Research and Development of Shanxi Province(2016NY-028)

Abstract: The maximum hydraulic conductivity in xylem of branches is one of the core indexes in plant water physiology research. The method of flush the stem by perfusing solution at higher pressure which dissolves and expels the emboli is the most commonly used method which be used to measure the hydraulic conductivity in xylem of stem segments. However, it is necessary to find a reliable method to obtain stable maximum hydraulic conductivity prior to experiment.In this study, the differentyears branches of Robinia pseudoacacia L. was used as the experimental materials, and we compared the effect of two different sample treatment methods on measuring hydraulic conductivity in xylem of stem segments(i.e., without soaked stem segments overnight with deionized water and soaked stem segments overnight with deionized water prior to experiment), the reliability of the maximum hydraulic conductivity determination was determined by test whether the maximum hydraulic conductivity in xylem of stem segments can be kept constant with increasing flushing time, and explore the effective method to improve the stability of measuring maximum hydraulic conductivity of branches. Our results demonstrated that:①the water conductivity of the branches that had not been soaked overnight with deionized water decreased linearly with increasing flushing time after the maximum hydraulic conductivity was reached by 150 kPa pressure flushing, while the hydraulic conductivity of the branches that had been soaked overnight with deionized water prior to experiment kept constant by the same experimental method. ②The hydraulic conductivity of two-year-old branches kept constant after 150 kPa pressure flushing, regardless of whether they were soaked overnight with deionized water or not. However, after soaking stems overnight with deionized water, the time required for two-year-old branches to reach the maximum hydraulic conductivity was significantly shorter than that of non-soaking treatment. ③According to the percentage of xylem area on the cross section of stem and the wood density of branches, the lignification degree of current-year branches was significantly lower than that of biennial branches during the experiment. We speculate that the decrease with increasing flushing time of hydraulic conductivity in the current-year's branches without soaked overnight is due to the blockage of vessel lumen caused by the secretion produced by mechanical injury of branches, and that soaked stem segments overnight with deionized water prior to experiment can effectively reduce the possibility of secretion being introduced into vessel lumen. Therefore, the soaking stem segments overnight with deionized water prior to experiment can improve the stability of maximum hydraulic conductivity measuring.

Key words: Robinia pseudoacacia L., hydraulic conductivity in xylem of stem segments, soak with deionized water, flushing time, different age branches

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